Cathode ray oscillograph



Patented Oct. 10, 1939 UN ED STATES GATHODE RAY OSOILLO GRAPH Theodore Mathieu Vogel, Paris, and Paul Traverse, Montrouge, France, assignors to Compagnie pour la Fabrication des Gompteurs et Materiel dUsines A Gaz, Montrouge, Seine,

France Application November 2, 1936, Serial No. 108,742 In France November 15, 1935 '7 Claims.

The present invention relates to improvements in the cathodes of cathode ray oscillographs of the cold cathode type.

In the apparatuses of this type hitherto known, it is, in fact, known that after a relatively short period of operation, for example of the order of several hours, the emission of electrified particles by the cathode ultimately brings about on its surface the formation of craters of the same form and nature as, but of smaller dimensions than, the craters of electric arcs. From this moment, the emission surface is impaired, and on the one hand the emission becomes irregular and much less intense, and on the other hand the concentration of the cathode beam (particularly in the space comprised between the cathode and the anode) becomes much more imperfect.

These drawbacks are particularly serious in non-detachable oscillographs such, for example, as those sealed like lamps, because they have the result of rendering such apparatuses practically useless after several hours of operation, and con sequently oppose their development.

The object of the present invention is to obviate the aforesaid drawbacks by reducing the emissive portion of the cathode to a small fraction of its total surface and displacing this emissive portion over practically the entire extent of the surface of the cathode. The invention also comprises means of bringing about, on the surface of the cathode, the displacement of its emissive portion, these means being automatic and not necessitating any mechanical connection between the cathode and the exterior of the oscillograph. According to the invention, this continuous or intermittent displacement, which may be uniform or irregular, is produced by rotation, translatory movement, by oscillations or finally by helicoidal movement of the cathode or of one or more screens interposed between the cathode and the anode.

The accompanying drawing shows, simply by way of example, which is not limitative with regard to the forms and dimensions, a number of constructional forms of the invention.

In Figure l, the cathode is constituted of a disc I disposed inside the cathode tube 2 and adapted to turn about a pin 3, for example under the action of the field of an induction member 4 disposed exteriorly of the tube 2. The anode 5 is eccentric with respect to the cathode l, and between these tWo electrodes there is disposed a screen 6 having an aperture '1. It is obvious that in the device according to this figure all the successive points of an annular zone 8 of radius R, traced on the surface of the cathode I, are successively utilised as emissive surfaces and that the aperture '5 of the screen 6 acts as a secondary cathode with respect to the anode.

In Figure 2, the cathode is constituted of a cylinder I I disposed inside the cathode tube l2 and adapted to be displaced by a helicoidal movement about a fixed pin l3 under the action of the field of an induction member I4 disposed exteriorly of the tube l2. The axis of the tube I2 is perpendicular to the pin l3. This tube encloses, on the one hand, the anode l5, and the other hand the screen I6 having the aperture ll therein. The cylinder forming the cathode II is connected with a member l8 having the screw required for bringing about its helicoidal displacement about the pin I 3, and adapted to be driven by the couple of the induction member Hi. In the device according to this figure, all the points of a spiral traced on the cylinder H are successively utilised as emissive surface. If the pith c of this spiral is sufficiently narrow, it will be seen that the device illustrated permits of successively utilizing all the zones of the lateral surface of the cylinder II as emissive surface. The aperture ll of the screen 16 acts as a secondary cathode with respect to the anode.

Finally, in Figure 3, the cathode is constituted of a movable disc 2| driven by an inductor 24a, While, under the action of the inductor 2%, a screen 29 having a spiral shaped aperture 3!] turns at a different speed. A second screen 26, which is fixed, has a slot 21 and is placed inside the tube 22, between the screen 29 and the anode 25. In order to ensure their driving by the inductors 2 3a. and 24b, the cathode 2| and the screen 29 may be connected to two small cylinders (not shown).

As a result of the rotation of the cathode and of the spiral in front of the fixed slot Zl, the emissive portion of the surface of the cathode 21 is displaced along successive spirals traced thereon. For suitable relative values of the speeds of the cathode and of the screen 29, the successive spirals may be juxtaposed, and practically the entire surface of the cathode 2| is finally utilised as emissive surface. The slot 21 of the screen 25 acts as a secondary cathode with respect to the anode and a condenser coil, not shown, permits of obviating the drawbacks attending the displacement of the emissive surface along the entire length of this slot 21.

A similar result may be obtained by keeping the cathode 2| fixed and making the screens 26 and 29 turn at different speeds.

With a View to simplification, the above figures do not show the method of action of the induction members 4, l4 and 24 on the members which they are intended to drive. This driving may be effected by any other known means without departing from the scope of the present invention. For example, the inductor is excited by polyphase windings and produces a rotary field, the body to be driven then consisting in a simple solid member, in the form of a cylinder w my or disc, or the inductor is excited with singlephase alternating current and the body to be driven provided with teeth along its periphery.

The whole functions as a synchronous motor with variable reluctance. However, in the latter case the addition of any of the known means for starting the movable members is provided.

In the same way, in the various forms of construction illustrated, the movable members are driven with a continuous or uniform movement, but the improvements forming the subject of the present invention are not limited to this case. In particular, the invention covers the possibility of providing, instead of a rotation, a setting in operation with an oscillatory movement of sufiicient amplitude. To this end, for example, the induction member is constituted by a simple electromagnet excited with alternating current, while the member to be driven is connected with a small permanent magnet.

In the device according to Figure 2, it is necessary for the helicoidal movement to be periodically reversed, for which purpose the invention provides for the periodical reversal of the connections of the induction member 14, this reversal being controlled, for example, by means of a synchronous motor feed by the same source as this inductor.

In a general manner, the scope of the invention will be considered as covering any cathode the emissive portion of which is displaced on its own surface automatically and without mechanical connections with the exterior of the oscillograph, irrespective of the means employed for obtaining this displacement and irrespective of the nature of this displacement. Theinvention in particular provides for the possibility of the electrode which forms the cathode, or one or more screens interposed between the cathode and the anode, being driven by electrostatic means, such as an electric fly, or simply oscillating, for example under the action of the force of gravity, its oscillatory movement being maintained or not by electrodynamic or electrostatic means.

The invention finally covers the possibility of the supplementary screen or screens provided above for forming the secondary cathode, being utilised at the same time to form a simple or compound electron lens, which may or may not comprise the primary emissive cathode.

What we claim is:

1. A cathode ray tube, comprising a bulb, an anode and a disc-shaped cathode within said bulb, a pin arranged within the bulb parallel to the longitudinal axis of the tube and perpendicularly traversing the centre of said disc to rotatably support the cathode, a screen between cathode and anode disposed parallel to said disc and having an aperture therein formed and arranged to expose only a fraction of the cathode surface for the emission of the cathode beam, and means provided externally of said bulb for continuously turning said cathode disc about said pin, so as to regularly and continuously displace the emitting spot along an annular line on the surface of said disc.

2. A cathode ray tube, comprising a bulb, an anode and a disc-shaped cathode within said bulb, a first disc-shaped screen rotatably arranged in said bulb between anode and cathode parallel to and coaxial within the latter and having a spiral slot therein, a second disc-shaped screen in said bulb between the anode and said first screen parallel to and coaxial with the same,

and having a substantially radial slot therein, the slots in said screen exposing only a fraction of the cathode surface for the emission of electrons, and means provided externally of said bulb for continuously imparting a rotary movement to said first screen, so as to regularly and continu ously displace the emitting spot on the surface of said cathode.

3. A cathode ray tube, as claimed in claim 2, in which said disc-shaped cathode is rotatably arranged in said bulb, and further means are provided externally of said bulb to continuously rotate said cathode disc simultaneously with the rotation of said first screen and at a different speed.

4. A cathode ray tube, as claimed in claim 2, in which said second screen is rotatably arranged in said bulb, and further means are provided externally of said bulb to continuously rotate said second screen simultaneously with the first one and at a different speed, the displacement of the emission spot on the cathode surface being defined by the relative displacement of the slots in the two screens relative to each other and to the cathode.

5. A cathode ray tube, comprising a bulb, an anode and a disc-shaped cathode within said bulb, a pin arranged within the bulb perpendicularly to said disc and coaxially with the same, a screen between cathode and anode disposed parallel to said disc and rotatably supported by the pin, an aperture in said screen to expose only a fraction of the cathode surface for the emission of electrons, and means provided externally of said bulb for continuously turning said screen about said pin, so as to regularly and continuously displace the emitting spot along an annular line of the surface of said disc.

6. A cathode ray tube, comprising a bulb, an anode and a disc-shaped cathode within said bulb, a pin arranged within the bulb parallel to the longitudinal axis of the tube and perpendicularly traversing the center of said disc to rotatably support the cathode, a screen between cathode and anode disposed parallel to said disc and having an aperture therein formed and arranged to expose only a fraction of the cathode surface for the emission of the cathode beam, and a stator including electric windings externally of said bulb for turning said rotor cathode disc about said pin, so as to displace the emitting spot along an annular line on the surface of said disc.

7. A cathode ray tube, comprising a bulb, an anode and a disc-shaped cathode within said bulb, a pin arranged within the bulb perpendicularly to said disc and coaxially with the same, a screen between cathode and anode disposed parallel to said disc and rotatably supported by the pin, an aperture in said screen to expose only a fraction of the cathode surface for the emission of electrons, and a stator provided with electric windings externally of said bulb for turning said screen about said pin so as to displace the emitting spot along an annular line on the surface of said disc.

THEODORE MATI-IIEU VOGEL. PAUL TRAVERSE. 

